This invention relates generally to universal joints and more particularly to cross and bearing assemblies for use in single and double cardan constant velocity universal joints as are used in automotive steering columns and other mechanical applications.
A common single cardan universal joint has two yokes, each of which has two ears with transverse bearing bores at a first end and a shaft attachment means at a second end for connection to some drive source such as a steering wheel or an automotive transmission and a driven object such as a steering gear or an automotive differential. The yokes are connected together by a cross and bearing assembly which consists of a body, commonly referred to as a spider or cross, with first and second orthogonal axes defined by four tenons projecting from a center portion outwardly on the axes.
The single cardan universal joint is assembled by fishing the tenons of the first axis of the spider into the bearing bores in the ears of one yoke, as seen in FIG. 5a, and pressing bearings into the bearing bores to fit over the tenons of the spider and to thereby position the spider both radially and axially in the yoke while permitting the spider to rotate within the yoke. The ears of the yoke must have bearing bores large enough and must be separated by a sufficient distance to permit the spider to be tilted enough to permit the tenons of the spider to be fished into the bearing bores. The universal joint is completed by repeating the assembly process on the second yoke and the tenons of the second axis of the spider. The resulting universal joint assembly is capable of flexing about the two orthogonal axes of the spider, or cross, which joins the two yokes together.
To provide constant velocity smooth rotary motion between shafts which lie in a common plane but have centerlines that are angularly displaced from each other, double cardan constant velocity joints are used. These consist of two single cardan universal joints, as described above, with a center housing substituted for the second yoke in each joint and a centering ball and socket added to the proximal ends of the first and second yokes, respectively. (Proximal with respect to the center housing.) The centering ball and socket assures that the angular misalignment between the two shafts will be equally divided about the center housing. The center housing has two pairs of bearing bores in ears at opposite ends, each pair of bores being aligned on an axis which is parallel to the axis of the other pair. The double cardan joint is assembled by attaching one pair of tenons of each of the two spiders to the ears at opposite ends of the center housing. This is usually done by pressing bearings on the tenons in the bearing bores of the ears of the center housing. The remaining tenons of each spider are attached to a yoke which is connected to a driving or driven member.
When used in automotive steering columns, both double cardan constant velocity joints and single cardan joints are difficult to install and connect because of the very limited space and visibility available under the dashboard and between the dash panel and the steering gear box. Because the ears of the yoke and center housing must support the bearings in which the tenons are pivoted, they must necessarily be thick enough that the bearings cannot rock when installed. They must also be wide enough to provide sufficient radial support for the bearing under the heaviest anticipated loads. This requires larger heavier yokes.
The added thickness and width requirements also extend to the ears of center housings of double cardan joints. Moreover, the diameter of the center housing must be larger to accommodate the greater thickness of the yokes and their ears. These requirements add to the weight and cost of the cardan joints and to the difficulty of fitting the cardan joints into the cramped quarters afforded by automotive design. Thus, the structural limitations imposed by the spider result in a size, weight, and cost penalty to the design of the automobile.
The foregoing illustrates limitations known to exist in present single and double cardan constant velocity joints for Use in automotive steering columns. Thus, it would clearly be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
In one aspect of the present invention, this is accomplished by providing a spider for use in a compact universal joint, said spider comprising a spider body having a hollow cylindrical portion and two opposed tenons projecting on a common axis radially outward from said hollow cylindrical portion, said hollow cylindrical portion being adapted for installation of bearings therein for pivotal support of said cross body on a pin mounted in a first yoke of said universal joint, and said tenons being adapted for mounting within bearings in a second yoke thereof.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.